The present invention relates to methods and apparatuses for cutting fiber-cement along an arcuate path.
The exteriors of houses and other types of buildings are commonly covered with siding materials that protect the internal structures from external environmental elements. The siding materials are typically planks or panels composed of wood, concrete, brick, aluminum, stucco, wood composites or fiber-cement composites. Wood siding is popular, but it is costly and flammable. Wood siding also cracks causing unsightly defects, and it is subject to infestation by insects. Aluminum is also popular, but it deforms easily, expands and contracts in extreme climates and is relatively expensive. Brick and stucco are also popular in certain regions of the country, but they are costly and labor-intensive to install.
Fiber-cements siding (FCS) offers several advantages compared to other types of siding materials. FCS is made from a mixture of cement, silica sand, cellulose and a binder. To form FCS siding products, a liquid fiber-cement mixture is pressed and then cured to form FCS planks, panels and boards. FCS is advantageous because it is non-flammable, weather-proof, and relatively inexpensive to manufacture. Moreover, FCS does not rot or become infested by insects. FCS is also advantageous because it may be formed with simulated wood grains or other ornamental designs to enhance the appearance of a building. To install FCS, a siding contractor cuts the panels or planks to a desired length at a particular job site. The siding contractor then abuts one edge of an FCS piece next to another and nails the cut FCS pieces to the structure.
After the FCS is installed, trim materials may be attached to the structure and the FCS may be painted.
Although FCS offers many advantages over other siding materials, it is difficult and expensive to cut. Siding contractors often cut FCS with a circular saw having an abrasive disk. Cutting FCS with an abrasive disk, however, generates large amounts of very fine dust that creates a very unpleasant working environment. Siding contractors also cut FCS with shears having opposing blades, as set forth in U.S. Pat. Nos. 5,570,678 and 5,722,386 which are herein incorporated by reference. Although the shears set forth in these patents cut a clean edge in FCS without producing dust, many siding contractors prefer to use a hand-held tool because they are accustomed to cutting siding with hand saws. Therefore, in light of the positive characteristics of FCS and the need for a hand-held cutting tool, it would be desirable to develop a hand-held cutting tool that quickly cuts clean edges through FCS without producing dust.
To meet the demand for a hand-held FCS cutting tool, the present inventors developed a hand-held tool with a reciprocating cutting blade (the xe2x80x9coriginal hand held-toolxe2x80x9d). The original hand-held tool had a motor-unit, a drive assembly coupled to the motor-unit to generate a reciprocating motion, and a blade set with a moving blade between first and second stationary fingers. The motor-unit was a 1046-90 Black and Decker(copyright) electric drill motor, and the drive assembly was a shear head manufactured by Kett Tool Co. of Cincinnati, Ohio. The moving blade was coupled to the Kett shear head to reciprocate between the first and second fingers. Additionally, the first and second fingers were spaced apart by 0.250 inches, and the cutting blade had a thickness of 0.185-0.200 inches. The sides of the cutting blade were accordingly spaced apart from the fingers by 0.025-0.0325 inches.
In the operation of the original hand-held tool, the fingers were placed on an FCS workpiece and the moving blade was driven from an open position below the workpiece to a closed position in the gap between the first and second fingers. As the blade moved from the open position to the closed position, it sheared the workpiece along both sides of the blade to form a cut in the workpiece approximately as wide as the gap between the first and second fingers. An operator would accordingly push the tool as the blade reciprocated between the open and closed positions to cut the workpiece.
One drawback of the original hand-held tool, however, was that the drive assembly and the motor-unit were subject to premature failure. One possible solution for reducing premature failure of the hand-held tool was to use stronger materials in the drive mechanism. Yet, using stronger materials would require more expensive metals that would increase the cost of the tools. Another possible solution for the original hand-held tool was to increase the size of the components of the motor unit and the drive mechanism. Using larger components, however, would increase the weight of the tools making them more difficult to handle. In addition to these constraints, cutting FCS without dust presents many challenges that are not present in other materials because FCS is a relatively brittle material that tends to crack along rough edges and unpredictable paths. As such, FCS cannot be cut with a thin blade unless it is in an opposing shear like those disclosed in U.S. Pat. Nos. 5,722,386 and 5,570,678. Thus, it would be desirable to develop a hand-held cutting tool that cuts a clean edge in FCS and is not subject to premature failure.
The present invention is directed toward methods and apparatuses for cutting fiber-cement materials. In one aspect of the invention, the apparatus can include a blade assembly for a reciprocating fiber-cement cutting tool. The assembly can include an alignment member attachable to the cutting tool. The alignment member generally has a first finger portion with a first guide surface and a first interior surface and a second finger portion with a second guide surface and a second interior surface. The first and second guide surfaces are positioned in a guide plane, and the first and second interior surfaces are spaced apart from one another. The blade assembly can further include a reciprocating cutting member between the first and second finger portions and movable relative to the finger portions and transverse to the guide plane between a first position and a second position. The cutting member can have a blade portion projecting from the guide plane and the blade portion can include a first side surface facing opposite the first interior surface and a second side surface facing opposite the second interior surface. The blade portion has a first axial dimension at a first location when intersected by the guide plane with the cutting member in the first position and a second axial dimension at a second location when intersected by the guide plane with the cutting member in the second position. The first axial dimension is approximately equal to the second axial dimension. In one aspect of the invention, the first and second axial dimensions can be approximately 0.250 inch. In another aspect of the invention, a lateral dimension of the blade portion when intersected by the guide plane can be approximately 0.250 inch. In yet another aspect of the invention, the blade assembly can be configured to rotate as a unit through an arc having a radius of less than three inches about an axis extending transverse to the guide plane.
The invention is also directed toward a method for severing fiber-cement materials. In one aspect of the invention, the method includes engaging a first surface of the fiber-cement with engaging surfaces of two spaced apart finger portions of a severing tool such that the engaging surfaces define a guide plane. The method can further include aligning a blade of the severing tool between the fingers of the tool with the blade facing a second surface of the fiber-cement opposite the first surface. The blade is reciprocated between the fingers in a direction transverse to the guide plane between a first position and a second position. The blade has an axial dimension defined by the intersection of the blade in the guide plane. The axial dimension of the blade is approximately the same when the blade is in both the first and second positions. A first portion of the fiber-cement is separated from a second portion of the fiber-cement along an arcuate path by turning the severing tool about an axis transverse to at least one of the first and second surfaces of the fiber-cement.